Protein phosphorylation, at specific amino acid residues, is important for the regulation of many cellular processes including cell cycle progression and division, signal transduction, and apoptosis. The phosphorylation is usually a transfer reaction of the terminal phosphate group from ATP to the protein substrate. The specific structure in the target substrate to which the phosphate is transferred is a tyrosine, serine or threonine residue. Since these amino acid residues are the target structures for the phosphoryl transfer, these protein kinase enzymes are commonly referred to as tyrosine kinases or serine/threonine (S/T) kinases. The phosphorylation reactions, and counteracting phosphatase reactions, on the tyrosine, serine and threonine residues are involved in countless cellular processes that underlie responses to diverse intracellular signals, regulation of cellular functions, and activation or deactivation of cellular processes. A cascade of protein kinases often participate in intracellular signal transduction and are necessary for the realization of cellular processes. Because of their ubiquity in these processes, the protein kinases can be found as an integral part of the plasma membrane or as cytoplasmic enzymes or localized in the nucleus, often as components of enzyme complexes. In many instances, these protein kinases are an essential element of enzyme and structural protein complexes that determine where and when a cellular process occurs within a cell. Given the importance and diversity of protein kinase function, it is not surprising that alterations in phosphorylation are associated with many diseases such as cancer, diabetes, inflammation, and hypertension.
The identification of effective small molecules that specifically inhibit protein kinases involved in abnormal or inappropriate cell proliferation, signaling, differentiation, protein production, or metabolism is therefore desirable. In particular, the identification of methods and compounds that specifically inhibit the function of kinases that are involved in immune modulation or proliferative disorders.
The present invention provides novel compounds that inhibit one or more S/T kinase or receptor or non-receptor tyrosine kinase. The compounds of the present invention affect cytokine inhibitory activity.
Cytokine mediated diseases and cytokine inhibition, suppression and antagonism are used in the context of diseases or conditions in which excessive or unregulated production or activity of one or more cytokine occurs. Examples of such cytokines are tumour necrosis factor alpha (TNFα), interleukin-1 (IL-1), interleukin-6 (IL-6) and interleukin-8 (IL-8). There remains a need for compounds which are useful in treating cytokine mediated diseases, and as such, inhibit, suppress or antagonize the production or activity of cytokines such as TNF, IL-1, IL-6 and IL-8.
The p38 MAP kinase (p38, also known as CSBP or SAPK) signaling pathway has been reported to be responsible for the expression of pro-inflammatory cytokines (such as TNF, IL-1, IL-6, IL-8) that are elevated in many inflammatory and auto-immune diseases (see J. C. Lee, Nature Reviews Drug Discovery 2003, 2, 717-726 and references cited therein). This pathway has been shown to be activated by cellular stressors, such as osmotic shock, UV light, free radicals, bacterial toxins, viruses, cytokines, chemokines and in response, mediates the expression of several cytokines including, but not limited to, TNF, IL-1, IL-6 and IL-8. In cells of myeloid lineage, such as macrophages and monocytes, both IL-1 and TNFα are transcribed in response to p38 activation. Subsequent translation and secretion of these and other cytokines initiates a local or systemic inflammatory response in adjacent tissue and through infiltration of leukocytes. While this response is a normal part of the physiological response to cellular stress, acute or chronic cellular stress leads to the excess or unregulated expression of pro-inflammatory cytokines. This, in turn, leads to tissue damage, often resulting in pain and debilitation. (see G. Panayi, N Engl J Med 2001, 344(12), 907; J. Smolen Nature Reviews Drug Discovery 2003, 2, 473 and references cited therein). The four known isoforms of p38 MAP kinase (p38 α, β, γ, δ) each showing different expression levels, tissue distributions and regulation, support the concept that they are involved in the etiology of many diseases.
Many solid tumours increase in mass through proliferation of malignant cells and stromal cells, including endothelial cells. In order for a tumor to grow lager than 2-3 mm in diameter, it must form a vasculature, a process known as angiogenesis. A selective p38 inhibitor has been shown to inhibit angiogenesis (see J. R. Jackson, J. Pharmacol Exp. Therpaeutics, 1998, 284, 687). Because angiogenesis is a critical component of the mass expansion of solid tumours, the development of new p38 kinase inhibitors for the inhibition of this process represents a promising approach for anti-tumour therapy. The compounds of the present invention are also useful in inhibiting growth of susceptible neoplasms (see R. M. Schultz, Potential of p38 MAP kinase inhibitors in the treatment of cancer. In: E. Jucker (editor), Progress in Drug Research 2003, 60, 59-92. The term “susceptible neoplasm” used in present application includes human cancers such as malignant melanoma, colorectal carcinoma, gastric carcinoma, breast carcinoma and non-small cell lung carcinoma.
Furthermore, inhibition of p38 kinase may be effective in treatment of certain viral conditions such as influenza (J. Immunology, 2000, 164, 3222), rhinovirus (J. Immunology, 2000, 165, 5211) and HIV (Proc. Nat. Acad. Sci., 1998, 95, 7422).
In summary, a number of inhibitors of p38 kinase are under active investigation for the treatment of a variety of disorders (Boehm, Adams Exp. Opin. Ther. Patents 2000, 10(1), 25-37. There remains a need for treatment in this field for compounds that are cytokine suppressive, i.e compounds that are capable of inhibiting p38 kinase.